我可以在父类中使用一个 Enum 作为 DiscriminatorType 和 Column 吗？答案

【问题标题】：Can I use one Enum as DiscriminatorType and Column in parent class?我可以在父类中使用一个 Enum 作为 DiscriminatorType 和 Column 吗？
【发布时间】：2021-04-24 10:22:44
【问题描述】：

我正在创建具有不同维修类型的维修服务。我有一个 SINGLE_TABLE 继承，我用 Enum repair_Type 区分它们，我还希望将 Repair_Type 作为一列，这样我就可以按类型对修复进行排序和搜索，但我得到了No enum constant 异常。

这是我的代码：

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(discriminatorType = DiscriminatorType.STRING)
public abstract class Repair {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public long repairID;

    @ManyToOne
    private Customer customerID;

    @Enumerated(EnumType.STRING)
    private RepairType repairType;

    @OneToMany
    private List<Employee> employeeList;

    @Enumerated(EnumType.STRING)
    private DeliveryOption deliveryOption;

    private boolean expressRepair;

    private boolean cleanProduct;

    @Column(length = 64)
    private String productImage;

    @OneToOne
    private Brand brand;

    private String model;

    private int size;

    private int buildYear;

    @Temporal(TemporalType.TIMESTAMP)
    private Date dateCreated;

    @Column(nullable = false)
    private String repairNote;
}
No getters and setters for brevity

修复类型：

public enum RepairType {
    KITE(Types.KITE),
    BOARD(Types.BOARD),
    BAR(Types.BAR),
    WETSUIT(Types.WETSUIT);

    private String type;

    RepairType(String type) {
    }

    public static class Types {
        public static final String KITE = "Kite";
        public static final String BOARD = "Board";
        public static final String BAR = "Bar";
        public static final String WETSUIT = "Wetsuit";
    }
}

子类修复类型示例（我有四个）

@Entity
@DiscriminatorValue(value = RepairType.Types.BAR)
public class BarRepair extends Repair {

    private boolean lengthCheck;

    public BarRepair() {
    }

    public BarRepair(long repairID, Customer customerID, List<Employee> employeeList, DeliveryOption deliveryOption, boolean expressRepair, boolean cleanProduct, String productImage, Brand brand, String model, int size, int buildYear, Date dateCreated, String repairNote, boolean lengthCheck) {
        super(repairID, customerID, employeeList, deliveryOption, expressRepair, cleanProduct, productImage, brand, model, size, buildYear, dateCreated, repairNote);
        this.lengthCheck = lengthCheck;
    }

    public boolean isLengthCheck() {
        return lengthCheck;
    }

    public void setLengthCheck(boolean lengthCheck) {
        this.lengthCheck = lengthCheck;
    }
}

【问题讨论】：

标签： java spring-boot hibernate jpa enums

【解决方案1】：

使用@Enumerated(EnumType.STRING) 映射的枚举使用枚举的.name() 表示进行映射。所以在你的情况下：KITE，BOARD，...

由于您将它们保存为Kite、Board 等，Hibernate ORM 无法找到每个 String 值的枚举。

我认为您需要使用@AttributeConverter：

@Converter
public static class RepairTypeConverter
        implements AttributeConverter<RepairType, String> {

    public Character convertToDatabaseColumn( RepairType value ) {
        if ( value == null ) {
            return null;
        }

        return value.getType();
    }

    public RepairType convertToEntityAttribute( String value ) {
        if ( value == null ) {
            return null;
        }

        return RepairType.fromType( value );
    }
}

其中getType() 和fromType() 用于将枚举转换为类型，反之亦然。

然后您可以使用以下方式映射属性：

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="repair_Type", discriminatorType = DiscriminatorType.STRING)
public abstract class Repair {
    ...
    
    @Convert( converter = RepairTypeConverter.class )
    @Column(name = "repair_Type)
    private RepairType repairType;

    ...
}

请参阅Hibernate ORM documentation for more details。

【讨论】：